In PC12 Cells Neurotoxicity Induced by Methamphetamine Is Related to Proteasome Inhibition

Differentially Expressed Nedd4-binding Protein Ndfip1 Protects Neurons Against Methamphetamine-induced Neurotoxicity

To identify factors involved in methamphetamine (METH) neurotoxicity, we comprehensively searched for genes which were differentially expressed in mouse striatum after METH administration using differential display (DD) reverse transcription-PCR method and sequent single-strand conformation polymorphism analysis, and found two DD cDNA fragments later identified as mRNA of Nedd4 (neural precursor cell expressed developmentally downregulated 4) WW domain-binding protein 5 (N4WBP5), later named Nedd4 family-interacting protein 1 (Ndfip1). It is an adaptor protein for the binding between Nedd4 of ubiquitin ligase (E3) and target substrate protein for ubiquitination. Northern blot analysis confirmed drastic increases in Ndfip1 mRNA in the striatum after METH injections, and in situ hybridization histochemistry showed that the mRNA expression was increased in the hippocampus and cerebellum at 2 h-2 days, in the cerebral cortex and striatum at 18 h-2 days after single METH administration. The knockdown of Ndfip1 expression with Ndfip1 siRNA significantly aggravated METH-induced neurotoxicity in the cultured monoaminergic neuronal cells. These results suggest that drastic increases in Ndfip1 mRNA is compensatory reaction to protect neurons against METH-induced neurotoxicity.

Lithium engages autophagy for neuroprotection and neuroplasticity: translational evidence for therapy

Here an overview is provided on therapeutic/neuroprotective effects of Lithium (Li⁺) in neurodegenerative and psychiatric disorders focusing on the conspicuous action of Li⁺ through autophagy. The effects on the autophagy machinery remain the key molecular mechanisms to explain the protective effects of Li⁺ for neurodegenerative diseases, offering potential therapeutic strategies for the treatment of neuropsychiatric disorders and emphasizes a crossroad linking autophagy, neurodegenerative disorders, and mood stabilization. Sensitization by psychostimulants points to several mechanisms involved in psychopathology, most also crucial in neurodegenerative disorders. Evidence shows the involvement of autophagy and metabotropic Glutamate receptors-5 (mGluR5) in neurodegeneration due to methamphetamine neurotoxicity as well as in neuroprotection, both in vitro and in vivo models. More recently, Li⁺ was shown to modulate autophagy through its action on mGluR5, thus pointing to an additional way of autophagy engagement by Li⁺ and to a substantial role of mGluR5 in neuroprotection related to neural e neuropsychiatry diseases. We propose Li⁺ engagement of autophagy through the canonical mechanisms of autophagy machinery and through the intermediary of mGluR5.

Methamphetamine-induced dopaminergic neurotoxicity as a model of Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disease with a high prevalence, approximately 1 % in the elderly population. Numerous studies have demonstrated that methamphetamine (MA) intoxication caused the neurological deficits and nigrostriatal damage seen in Parkinsonian conditions, and subsequent rodent studies have found that neurotoxic binge administration of MA reproduced PD-like features, in terms of its symptomatology and pathology. Several anti-Parkinsonian medications have been shown to attenuate the motor impairments and dopaminergic damage induced by MA. In addition, it has been recognized that mitochondrial dysfunction, oxidative stress, pro-apoptosis, proteasomal/autophagic impairment, and neuroinflammation play important roles in inducing MA neurotoxicity. Importantly, MA neurotoxicity has been shown to share a common mechanism of dopaminergic toxicity with that of PD pathogenesis. This review describes the major findings on the neuropathological features and underlying neurotoxic mechanisms induced by MA and compares them with Parkinsonian pathogenesis. Taken together, it is suggested that neurotoxic binge-type administration of MA in rodents is a valid animal model for PD that may provide knowledge on the neuropathogenesis of PD.

Translational evidence for lithium-induced brain plasticity and neuroprotection in the treatment of neuropsychiatric disorders

Increasing evidence indicates lithium (Li+) efficacy in neuropsychiatry, pointing to overlapping mechanisms that occur within distinct neuronal populations. In fact, the same pathway depending on which circuitry operates may fall in the psychiatric and/or neurological domains. Li+ restores both neurotransmission and brain structure unveiling that psychiatric and neurological disorders share common dysfunctional molecular and morphological mechanisms, which may involve distinct brain circuitries. Here an overview is provided concerning the therapeutic/neuroprotective effects of Li+ in different neuropsychiatric disorders to highlight common molecular mechanisms through which Li+ produces its mood-stabilizing effects and to what extent these overlap with plasticity in distinct brain circuitries. Li+ mood-stabilizing effects are evident in typical bipolar disorder (BD) characterized by a cyclic course of mania or hypomania followed by depressive episodes, while its efficacy is weaker in the opposite pattern. We focus here on neural adaptations that may underlie psychostimulant-induced psychotic development and to dissect, through the sensitization process, which features are shared in BD and other psychiatric disorders, including schizophrenia. The multiple functions of Li+ highlighted here prove its exceptional pharmacology, which may help to elucidate its mechanisms of action. These may serve as a guide toward a multi-drug strategy. We propose that the onset of sensitization in a specific BD subtype may predict the therapeutic efficacy of Li+. This model may help to infer in BD which molecular mechanisms are relevant to the therapeutic efficacy of Li+.

Autophagy as a gateway for the effects of methamphetamine: From neurotransmitter release and synaptic plasticity to psychiatric and neurodegenerative disorders

As a major eukaryotic cell clearing machinery, autophagy grants cell proteostasis, which is key for neurotransmitter release, synaptic plasticity, and neuronal survival. In line with this, besides neuropathological events, autophagy dysfunctions are bound to synaptic alterations that occur in mental disorders, and early on, in neurodegenerative diseases. This is also the case of methamphetamine (METH) abuse, which leads to psychiatric disturbances and neurotoxicity. While consistently altering the autophagy machinery, METH produces behavioral and neurotoxic effects through molecular and biochemical events that can be recapitulated by autophagy blockade. These consist of altered physiological dopamine (DA) release, abnormal stimulation of DA and glutamate receptors, as well as oxidative, excitotoxic, and neuroinflammatory events. Recent molecular insights suggest that METH early impairs the autophagy machinery, though its functional significance remains to be investigated. Here we discuss evidence suggesting that alterations of DA transmission and autophagy are intermingled within a chain of events underlying behavioral alterations and neurodegenerative phenomena produced by METH. Understanding how METH alters the autophagy machinery is expected to provide novel insights into the neurobiology of METH addiction sharing some features with psychiatric disorders and parkinsonism.

Morphology, clearing efficacy, and mTOR dependency of the organelle autophagoproteasome

The interplay between autophagy (ATG) and ubiquitin proteasome (UP) cell-clearing systems was recently evidenced at biochemical and morphological levels, where subunits belonging to both pathways co-localize within a novel organelle named autophagoproteasome (APP). We previously documented that APP occurs at baseline conditions, while it is hindered by neurotoxicant administration. This is bound to the activity of the mechanistic target of rapamycin (mTOR), since APP is stimulated by mTOR inhibition, which in turn, is correlated with cell protection. In this brief report, we provide novel morphological and biochemical evidence on APP, suggesting the presence of active UP subunits within ATG vacuoles. Although a stream of interpretation considers such a merging as a catabolic pathway to clear inactive UP subunits, our data further indicate that UP-ATG merging may rather provide an empowered catalytic organelle.

mTOR Modulates Methamphetamine-Induced Toxicity through Cell Clearing Systems

Methamphetamine (METH) is abused worldwide, and it represents a threat for public health. METH exposure induces a variety of detrimental effects. In fact, METH produces a number of oxidative species, which lead to lipid peroxidation, protein misfolding, and nuclear damage. Cell clearing pathways such as ubiquitin-proteasome (UP) and autophagy (ATG) are involved in METH-induced oxidative damage. Although these pathways were traditionally considered to operate as separate metabolic systems, recent studies demonstrate their interconnection at the functional and biochemical level. Very recently, the convergence between UP and ATG was evidenced within a single organelle named autophagoproteasome (APP), which is suppressed by mTOR activation. In the present research study, the occurrence of APP during METH toxicity was analyzed. In fact, coimmunoprecipitation indicates a binding between LC3 and P20S particles, which also recruit p62 and alpha-synuclein. The amount of METH-induced toxicity correlates with APP levels. Specific markers for ATG and UP, such as LC3 and P20S in the cytosol, and within METH-induced vacuoles, were measured at different doses and time intervals following METH administration either alone or combined with mTOR modulators. Western blotting, coimmunoprecipitation, light microscopy, confocal microscopy, plain transmission electron microscopy, and immunogold staining were used to document the effects of mTOR modulation on METH toxicity and the merging of UP with ATG markers within APPs. METH-induced cell death is prevented by mTOR inhibition, while it is worsened by mTOR activation, which correlates with the amount of autophagoproteasomes. The present data, which apply to METH toxicity, are also relevant to provide a novel insight into cell clearing pathways to counteract several kinds of oxidative damage.

Epigenetic Effects Induced by Methamphetamine and Methamphetamine-Dependent Oxidative Stress

Methamphetamine is a widely abused drug, which possesses neurotoxic activity and powerful addictive effects. Understanding methamphetamine toxicity is key beyond the field of drug abuse since it allows getting an insight into the molecular mechanisms which operate in a variety of neuropsychiatric disorders. In fact, key alterations produced by methamphetamine involve dopamine neurotransmission in a way, which is reminiscent of spontaneous neurodegeneration and psychiatric schizophrenia. Thus, understanding the molecular mechanisms operated by methamphetamine represents a wide window to understand both the addicted brain and a variety of neuropsychiatric disorders. This overlapping, which is already present when looking at the molecular and cellular events promoted immediately after methamphetamine intake, becomes impressive when plastic changes induced in the brain of methamphetamine-addicted patients are considered. Thus, the present manuscript is an attempt to encompass all the molecular events starting at the presynaptic dopamine terminals to reach the nucleus of postsynaptic neurons to explain how specific neurotransmitters and signaling cascades produce persistent genetic modifications, which shift neuronal phenotype and induce behavioral alterations. A special emphasis is posed on disclosing those early and delayed molecular events, which translate an altered neurotransmitter function into epigenetic events, which are derived from the translation of postsynaptic noncanonical signaling into altered gene regulation. All epigenetic effects are considered in light of their persistent changes induced in the postsynaptic neurons including sensitization and desensitization, priming, and shift of neuronal phenotype.

Proteomic analysis of saliva in HIV-positive heroin addicts reveals proteins correlated with cognition

The prevalence of HIV-associated neurocognitive disorders (HAND) remains high despite effective antiretroviral therapies. Multiple etiologies have been proposed over the last several years to account for this phenomenon, including the neurotoxic effects of antiretrovirals and co-morbid substance abuse; however, no underlying molecular mechanism has been identified. Emerging evidence in several fields has linked the gut to brain diseases, but the effect of the gut on the brain during HIV infection has not been explored. Saliva is the most accessible gut biofluid, and is therefore of great scientific interest for diagnostic and prognostic purposes. This study presents a longitudinal, liquid chromatography-mass spectrometry-based quantitative proteomics study investigating saliva samples taken from 8 HIV-positive (HIV⁺), 11 −negative (HIV⁻) heroin addicts. In addition, saliva samples were investigated from 11 HIV⁻, non-heroin addicted healthy controls. In the HIV⁺ group, 58 proteins were identified that show significant correlations with cognitive scores, implicating disruption of protein quality control pathways by HIV. Notably, only one protein from the HIV⁻ heroin addict cohort showed a significant correlation with cognitive scores, and no proteins correlated with cognitive scores in the healthy control group. In addition, the majority of correlated proteins have been shown to be associated with exosomes, allowing us to propose that the salivary glands and/or oral epithelium may modulate brain function during HIV infection through the release of discrete packets of proteins in the form of exosomes.

Does 1-(R)-aminoindan possess neuroprotective properties against experimental Parkinson's disease?

The anti-Parkinsonian, monoamine oxidase-B inhibitor drug, rasagiline (Azilect®), is primarily metabolized by hepatic cytochrome P450 isoenzyme 1A2-mediated N-dealkylation to form its major metabolite, 1-(R)-aminoindan. The present study was undertaken to further investigate, for the first time, the possible neuroprotective effect of 1-(R)-aminoindan in two rat models of Parkinson's disease, the 6-hydroxydopamine- and lactacystin (a proteasomal inhibitor)-induced nigrostriatal degeneration. 1-(R)-aminoindan reversed behavioral asymmetry and restored striatal catecholamine levels in these two rat models and significantly protected neurons from hydrogen peroxide-induced oxidative stress. These observations indicate that 1-(R)-aminoindan may contribute to the overall neuroprotective activity of its parental compound, rasagiline.

Methamphetamine toxicity and messengers of death

Methamphetamine (METH) is an illicit psychostimulant that is widely abused in the world. Several lines of evidence suggest that chronic METH abuse leads to neurodegenerative changes in the human brain. These include damage to dopamine and serotonin axons, loss of gray matter accompanied by hypertrophy of the white matter and microgliosis in different brain areas. In the present review, we summarize data on the animal models of METH neurotoxicity which include degeneration of monoaminergic terminals and neuronal apoptosis. In addition, we discuss molecular and cellular bases of METH-induced neuropathologies. The accumulated evidence indicates that multiple events, including oxidative stress, excitotoxicity, hyperthermia, neuroinflammatory responses, mitochondrial dysfunction, and endoplasmic reticulum stress converge to mediate METH-induced terminal degeneration and neuronal apoptosis. When taken together, these findings suggest that pharmacological strategies geared towards the prevention and treatment of the deleterious effects of this drug will need to attack the various pathways that form the substrates of METH toxicity.

Comparison of neuroprotective and neurorestorative capabilities of rasagiline and selegiline against lactacystin-induced nigrostriatal dopaminergic degeneration

Nigrostriatal neurodegeneration in Parkinson's disease (PD) has been postulated to be caused by various pathological conditions, such as mitochondrial defects, oxidative stress, and ubiquitin-proteasome system (UPS) dysfunction. Pharmacological strategies designed to interfere with these pathological pathways may effectively counteract the degeneration. Rasagiline and selegiline are selective and irreversible monoamine oxidase-B inhibitors that possess significant protective properties on dopamine neurons in various pre-clinical models of PD. In the present study, the neuroprotective and neurorestorative effects of rasagiline and selegiline were compared in an animal model of PD produced by inhibition of the UPS. C57BL/6 male mice were microinjected bilaterally with UPS inhibitor lactacystin (1.25 mug/side), into the medial forebrain bundle. Administration of rasagiline (0.2 mg/kg, i.p. once per day) or selegiline (1 mg/kg, i.p. once per day), started 7 days before or after (up to 28 days) after lactacystin microinjection. We found that both rasagiline and selegiline exerted a significant neuroprotective effect against lactacystin-induced neurodegeneration; but only rasagiline managed to restore the nigrostriatal degeneration. Furthermore, rasagiline showed a modest protection against lactacystin-induced inhibition of proteasomal activity. Our study indicates that compared with selegiline, rasagiline is more potent in protecting neurodegeneration induced by UPS impairment and may, therefore, exert disease-modifying effects in PD.

Neurotoxins and neurotoxicity mechanisms. an overview

Neurotoxins represent unique chemical tools, providing a means to 1) gain insight into cellular mechanisms of apopotosis and necrosis, 2) achieve a morphological template for studies otherwise unattainable, 3) specifically produce a singular phenotype of denervation, and 4) provide the starting point to delve into processes and mechanisms of nerve regeneration and sprouting. There are many other notable uses of neurotoxins in neuroscience research, and ever more being discovered each year. The objective of this review paper is to highlight the broad areas of neuroscience in which neurotoxins and neurotoxicity mechanism come into play. This shifts the focus away from neurotoxins per se, and onto the major problems under study today. Neurotoxins broadly defined are used to explore neurodegenerative disorders, psychiatric disorders and substance use disorders. Neurotoxic mechanisms relating to protein aggregates are indigenous to Alzheimer disease, Parkinson's disease. NeuroAIDS is a disorder in which microglia and macrophages have enormous import. The gap between the immune system and nervous system has been bridged, as neuroinflammation is now considered to be part of the neurodegenerative process. Related mechanisms now arise in the process of neurogenesis. Accordingly, the entire spectrum of neuroscience is within the purview of neurotoxins and neurotoxicity mechanisms. Highlights on discoveries in the areas noted, and on selective neurotoxins, are included, mainly from the past 2 to 3 years.